RF communications systems typically communicate using at least one of three different modes of operation. The first mode, called simplex, is a one-way mode of operation, in which a transmitter from one location transmits data to a receiver at another location. For example, a broadcast radio station transmits data one-way to radios. The second mode, called half duplex, is a two-way mode of operation, in which a first transceiver communicates with a second transceiver; however, only one transceiver transmits at a time. Therefore, the transmitter and receiver in a transceiver do not operate simultaneously. For example, certain telemetry systems operate in a send-then-wait-for-reply manner. The third mode, called full duplex, is a simultaneous two-way mode of operation, in which a first transceiver communicates with a second transceiver, and both transceivers may transmit simultaneously; therefore, the transmitter and receiver in a transceiver must be capable of operating simultaneously. For example, certain cellular telephone systems operate using a full duplex mode of operation.
Some communications protocols, such as Universal Mobile Telecommunications System (UMTS) or wideband code division multiple access (WCDMA) protocols may require RF receivers to receive RF signals continuously. Further, some protocols may require down conversion to a very low intermediate frequency (VLIF) or may require direct conversion receive (DCR) down conversion. In VLIF down conversion, a frequency of a local oscillator (LO) signal is near a frequency of a carrier of an RF receive signal, and in DCR conversion, the frequency of the LO signal may be equal to the frequency of the carrier of the RF receive signal. As a result, DC offsets in down conversion circuitry may become quite significant. Further, due to receiving RF signals continuously, as mandated by certain RF communications protocols, there may be insufficient time to perform DC offset correction. Thus, there is a need to perform DC offset correction quickly in real time.